1. Technical Field
The present invention relates to a resonator element, a resonator, an oscillator, an electronic apparatus, and a moving object.
2. Related Art
An AT cut resonator element has thickness shear vibration as a vibration mode of main vibration for excitation, and is suitable for miniaturization and achievement of high frequency. In addition, the AT cut resonator element shows a third-order curve which is superior in frequency-temperature characteristics, and is thus used for various applications such as piezoelectric oscillators and electronic apparatuses.
JP-A-58-047316 discloses a so-called “mesa type” AT cut resonator element in which a convex surface is provided at a center. Such a mesa type AT cut resonator element is advantageous in that energy confinement efficiency is high. JP-UM-A-6-052230 discloses a mesa type AT cut quartz crystal resonator in which a boundary portion between a convex portion at a center and a thin portion therearound is a tilt surface or a curved surface. This configuration has an advantage in that sub-vibration can be minimized by reducing a crystal impedance (CI) value. However, in the AT cut resonator elements disclosed in JP-A-58-047316 and JP-UM-A-6-052230, there is a case where spurious caused by flexural vibration which is an unwanted vibration mode may not be sufficiently reduced.